Many integrated circuit devices support both logical and arithmetic operations. In some forms of integrated circuit devices, particularly PLDs such as FPGAs, logic is provided that can be configured for different kinds of operations. Commonly-assigned U.S. Pat. No. 7,565,388, which is hereby incorporated by reference herein in its entirety, describes a programmable device having logic blocks including lookup-table based logic elements that can be configured to perform logical and arithmetic operations. In arithmetic mode, those logic elements could be configured to perform binary addition, among other functions, or, by selecting, as an input to a dedicated adder in one logic element, a signal from another logic element, to perform ternary addition.